Actuators such as those used to adjust seat position within a vehicle may include an electric motor and a gear set disposed between the drive motor and seat that transmits the output of the motor to the vehicle seat. The gear set may be disposed in a housing having separable components such as a container and a cover that are assembled together after the gear set has been installed therein. The housing components are maintained in the assembled configuration using mechanical fasteners, adhesives, welding or other fastening techniques. Use of snap-fit mechanical fasteners can be advantageous since the snap fit fastener components may be formed integrally with the corresponding housing components in an injection molding process and since housing assembly is simple and can be performed without tools. However, in some embodiments, the snap fit fastener components may protrude from edge portions of the housing container and cover. During handling of the gear housing components, for example during assembly of the gear set and/or during assembly of the gear housing components, the snap fit fastener components may be loaded and can break, which results in reduced manufacturability.
In some actuators, the gear set includes a worm gear that is driven by a pinion mounted on the motor output shaft. In use, the worm gear may generate forces on the housing in a direction that tends to separate the cover from the container, for example in a direction parallel to the rotational axis of the worm gear. In some embodiments, the generated forces are sufficient to require five or six fasteners between the lid and the container in order for the cover to be retained on the container. The large number of fasteners increases the likelihood of damage during handling, and the effort of measurement during production and quality assurance is more difficult and expensive than for housings having fewer such fasteners. In addition, the worm gear is supported on and rotates about a gear shaft that is spaced apart from the gear housing sidewalls. The distance between the location of force application at the gear shaft and the fasteners at the gear housing sidewalls may result in an undesirable and/or excessive deflection of the cover.
A need exists for an actuator housing that has fasteners that securely join the housing components, are unlikely to be damaged during handling and assembly, and minimize the number of fasteners that are required to maintain the housing components in an assembled configuration without undesirable deflection of the housing components.